Not to unlearn what you have learned is the most necessary kind of learning.

Some suggestions for you :

The most useful piece of learning for the uses of life is to unlearn what is untrue.

I am sadly afraid that I must have done some wicked thing.

Pay attention to your enemies, for they are the first to discover your mistakes.

As iron is eaten away by rust, so the envious are consumed by their own passion.

Quarrels often arise in marriages when the bridal gifts are excessive.

The investigation of the meaning of words is the beginning of education.

The most necessary learning is that which unlearns evil.

There are only two people who can tell you the truth about yourself - an enemy who has lost his temper and a friend who loves you dearly.

When brothers agree, no fortress is so strong as their common life.

As iron is eaten by rust, so are the envious consumed by envy.